The synthesis, turnover, and function of intestinal brush border proteins will continue to be studied. The specific proteins currently under investigation are alkaline phosphatase in suckling rats, intrinsic factor (IF-B12) receptor in dog ileum, apolipoproteins in rat and human jejunum. We will study the incorporation of alkaline phosphatase in the cell cytosol and the membrane. Changes in synthesis of phosphatase with fat feeding and vitamin D stimulation will be studied, along with determination of serum half-life, so that static measurements of serum phosphatase can be better interpreted. Human intestinal phosphatase will be purified and an immunoassay to it developed. The intrinsic factor receptor will be purified to determine its structure and relationship to lipids, and to ascertain how IF and B12 are dissociated from the complex.